The present invention relates to a power jack for use in portable electronic/electrical equipment, for instance.
Portable equipment such as a portable tape recorder usually works on a battery. In places where a commercial power supply system is available, it is customary to use an adaptor to feed therefrom DC power to a power jack of the portable equipment.
FIG. 1 schematically depicts the construction of a conventional power jack of this kind. The power jack has a body 11 of an insulating material, in which a conductive pin 12 and a movable contact piece or strip 13 are provided. The body 11 has in its front a plug insertion hole 14. The conductive pin 12 is planted on the inside of a rear end wall of the body 11, and extends forwardly thereof in alignment with the center axis of the plug insertion hole 14. A terminal 15 is attached to the rear end of the conductive pin 12 extending out from the body 11.
The movable contact piece 13, which extends in a direction of from front to rear of the body 11, has its forward end portion bent to form a base portion 16 that extends along the inner wall surface of the bottom of the body 11. A terminal 17 formed integrally with the base portion 6 is extended to the outside of the body 11. The movable conductor piece 13 further has its intermediate portion extended toward the conductive pin 12 and then bent gently into a shallow, inverted V-letter shape. The free end of the movable contact piece 13 is held in resiliently biased engagement with the rear end face of the body 11 on the inside thereof.
As a power plug (not shown) is fitted into the plug insertion hole 14, the movable contact piece 13 comes into contact with a cover conductor forming the cylindrical peripheral surface of the power plug, and at the same time, the conductive pin 12 gets into engagement with a contact in the plug, thus establishing electric connection between the plug and jack.
With the conventional power jack of the above construction, however, the movable contact piece 13 makes a one-point contact with the cover conductor of the mating plug, and hence they are readily forced out of contact by vibration or prying--this gives rise to the problems of possible short breaks and a poor retention force for retaining the power plug. Another problem is that the one-point contact structure of an extremely small contact area inevitably lowers the current carrying capacity of the power jack, resulting in a severely limited allowable current value.